Storage tanks for liquids, such as petroleum products, utilizing an internal floating cover for such liquids have been known for a long period of time and, subject to minor variations in construction, have long been reasonably well standardized. Included within such standardized construction is a floating cover for the liquid product stored therein which cover floats on top of such liquid and rises and falls with the upper surface thereof. Such cover is normally provided with a plurality of legs affixed thereto in any of several well-known ways. Said legs extend below such cover for engaging the floor of the tank when the liquid is either absent therefrom or is sufficiently low as not to lift said cover a minimum distance from said floor.
Said floors have long been made from the same material as that from which the tank is made, which may be either steel or aluminum, and which for corrosion resistant purposes along with the remaining interior of the tank, is then coated with a vinyl, epoxy, or other appropriate plastics which are inert to the product, as a petroleum product, to be received into said tank. When said cover is in a lowermost position, said legs rest on said bottom under such conditions that they often scratch same or even gouge it sufficiently, particularly after repeated operations, as to permit the liquid product to contact the metal bottom, corrode same and permit leakage. Inasmuch as such leakage must be prevented regardless of cost for well-known reasons both economic and environmental, the present practice is to drain the tank periodically and recoat the bottom thereof, thus requiring the recoating of the entire bottom to effect repair of only scattered wear and/or scratch or gouge marks.
This procedure is reasonably effective and has gone into widespread use. However, it is expensive and takes a given tank out of use for longer than required for mere cleaning.
This situation has caused severe maintenance problems in connection with such tanks and it has long been highly desirable to provide a simple but effective means for preventing such scratching or gouging of the bottom of such tanks.